In recent years, a number of digital contract systems have been proposed to encourage the production, distribution, and sale of high-quality digital works over networks, such as the Internet. These systems allow rights, fees, and other terms and conditions to be associated with a given work. Combined with proposed secure software and hardware, digital contracts can be enforced to insure proper payment and rights management for digital works. Of course, there are many potential vulnerabilities at the software and hardware levels that an attacker could exploit to subvert a digital contract system. In particular, security problems can arise even when the system is assumed to protect content and enforce contracts as specified.
Systems to enforce digital contracts are already in place or may be available soon. For instance, examples of such systems are set forth by M. Stefik and A. Silverman, “The Bit And the Pendulum: Balancing the Interests of Stake-holders in Digital Publishing”, The Computer Lawyer, Vol. 16, pp. 1-15, 1999; ContentGuard: Rights Protection from Xerox, http://www. contentguard.com/; Intertrust Digital Rights Management, http: //www. intertrust.com/; and The Secure Digital Music Initiative, http: //www. sdmi. org/ which are each incorporated herein by reference in their entirety.
In operation, these kinds of systems are capable of being used to support relatively simple business models. Such business models do not involve middlemen, who buy digital content from one or more providers, repackage or otherwise add value, and then resell to consumers or to other middlemen. It is expected that in the near future middlemen may be prevalent in the digital work business. Every middleman in a distribution chain produces a new contract to enforce a new set of terms and conditions. For long distribution chains, it may be unwieldy to carry along every contract that was created along the way. This would be undesirable from a practical business perspective as well. The seller has a strong incentive to conceal from the buyer earlier contracts along a chain. If a potential buyer gets to see earlier contracts, the buyer might be tempted to renegotiate the new contract at more favorable terms, or “disintermediate” the seller and negotiate independently with earlier sellers in the chain. There is a natural privacy requirement here that may be crucial for creating viable business niches.
There is a natural integrity requirement that is also fundamental. A middleman may wish to keep secret the favorable terms of earlier contracts in a distribution chain, but he may not be allowed to negotiate a new contract that violates his existing obligations. As a result of adding value to a digital work, a reseller is certainly entitled to be compensated by raising the fees associated with use of the content. Other terms associated with the earlier contract might be altered by a reseller as well. Expiration dates might be moved up, or hardware security requirements might be tightened, or payment options might shift (e.g., from flat rates to per-use fees). Any changes that are made in the new contract may in some sense be “faithful” to, or in other words, consistent with the original contract —existing payment obligations may not decrease, expiration dates may not move into the future, new rights cannot be granted, and so on.
These two requirements are in conflict with each other. Verifying that a new contract is faithful to an old contract seems to require that both contracts be inspected by the new buyer, but that would violate the privacy needs of the seller. There is thus a need for a cryptographic approach to balance distribution chain privacy and distribution chain integrity.
A system, method and article of manufacture are provided for certifying contracts utilizing a network. Initially, a first and second contract is received utilizing a network. Each contract includes a plurality of terms. It is then certified that the terms of the second contract are consistent with the terms of the first contract. This provides distribution chain integrity in accordance with one of the objectives of the present invention.
In one embodiment of the present invention, received with the contacts is proof that the terms of the second contract are consistent with, or “faithful” to the terms of the first contract. As such, the certification may be based on the proof. As an option, the proof may be generated by comparing the terms of the first and second contract.
In one embodiment of the present invention, received with the contracts is proof that the terms of the second contract are consistent with, or “faithful” to the terms of the first contract. As such, the certification may be based on the proof. As an option, the proof may be generated by comparing the terms of the first and second contract.
In yet another embodiment of the present invention, the first contract may be received with a certifier indicating that the terms of the first contract are consistent with terms of a previous contract. Optionally, at least a portion of the terms of at least one of the contracts is obfuscated, and the second contract may be sent with obfuscated terms utilizing the network. This provides distribution chain privacy in accordance with one of the objectives of the present invention.
In one aspect of the present invention, a system, method and article of manufacture may be provided for obfuscating terms of a document in order to provide distribution chain privacy. In operation, a document, i.e. contract, may be received including a plurality of terms. Once received, at least one of the terms of such document may be identified. As such, the identified term of the document may be obfuscated. This feature may be particularly beneficial when giving a party the document when one wants to retain some of the tenms thereof as confidential.
In one embodiment of the instant aspect, the contract may be received from a first party, and further sent to a second party with the at least one obfuscated term utilizing a network. As an option, the at least one term of the contract may be identified based on a list of terms.
In this way, the present invention demonstrates an extremely efficient solution to the problem of distribution chain security, and thus extend the realm of real-world settings for which zero-knowledge proof techniques are practical. These and other advantages of the present invention may become apparent upon reading the following detailed description and studying the various figures of the drawings.